A polycarbonate (PC) resin collectively refers to polymeric compounds having a carbonate ester structure with balanced impact strength and tensile strength and has excellent mechanical properties and a small variation in strength with temperature and thus has been widely used in various fields of machinery, electrics, components, helmets, engineering plastic, automobiles, and the like. However, PC is a thermoplastic resin without resistance to fire. Therefore, various studies have been conducted to impart flame retardancy to the PC resin.
Conventionally, a technology of mixing a halogenated flame retardant and antimony oxide has been usually used to impart flame retardancy to the PC resin. The halogenated flame retardant shows excellent flame retardancy but generates a gas adversely affecting humans and the environment during combustion. Therefore, a flame retardation technology using non-halogenated compounds is needed.
A flame retardation technology for polymer resins including inorganic compounds such as magnesium hydroxide, aluminum hydroxide, etc., as flame retardants using non-halogenated compounds has been suggested. Japanese Patent Laid-open Publication No. 10-204276 discloses a method of imparting flame retardancy to a resin by mixing aluminum hydroxide and one or more nitrogen compounds and red phosphorus and adding the mixture into an unsaturated polyester resin. However, the need for use of a large amount of aluminum hydroxide results in degradation of mechanical properties of a resin composition. Further, Korean Patent Laid-open Publication No. 2007-0064924 uses a brominated organic compound as an acrylonitrile-butadiene-styrene copolymer resin (ABS resin) which is not environment-friendly.
In general, the kind of a flame retardant to impart optimum flame retardancy varies depending on the kind of a resin. For example, if magnesium hydroxide is used as a flame retardant for an ABS resin, it cannot serve as a proper flame retardant due to chemical reaction during combustion. However, antimony oxide has been used as a retardant having the highest flame-retardant effect. Meanwhile, if magnesium hydroxide which is not proper for the ABS resin is used as a flame retardant for an acrylic resin, the highest flame-retardant effect can be obtained, and in this case, antimony oxide does not have a significant flame-retardant effect (Haekyung Park, Study on Flame Retardancy of Plastic Resin Depending on Kind of Flame Retardant, Korean Institute of Fire Science & Engineering Joint Fall Conference Proceedings 2005).
In recent years, resorcinol bis(diphenyl phosphate) (RDP), bisphenol A bis(diphenyl phosphate) (BDP), triphenyl phosphate (TPP), etc. have been widely used as phosphorous flame retardants. Particularly, RDP has low molecular weight and viscosity but has a high phosphorus (P) content, and, thus, even if a small amount of RDP is mixed in a PC resin, it is possible to obtain high flame retardancy and high fluidity. Further, the softening temperature can be reduced by about 10° C. to about 20° C., and, thus, the processing temperature can be reduced. Such a reduction in processing temperature enables the manufacturing of a high-quality product in a mold having a complicated structure and suppresses various side effects, such as mold deposition, occurring when molding is performed at a high temperature for a long time.
However, the use of a large amount of flame retardant results in degradation of optical or mechanical properties, and the use of a small amount of flame retardant makes it difficult to obtain desired flame retardancy.
Korean Patent No. 10-1738740 which is the background technology of the present disclosure relates to a halogen-free transparent flame retardant polycarbonate resin composition and a molded product. However, this prior art does not describe biphenyl cyclic 1,3-propanediol phosphate which is a novel non-halogenated flame retardant.